Heat-exchanger module

ABSTRACT

A tube bundle for the circulation of a first fluid is disposed within a shell for the circulation of a second fluid. At least one end of the tube bundle has a rectilineal portion followed by expansion-bends for compensating differential expansions. The tubes are subdivided in the vicinity of the rectilineal portion into two half-bundles each disposed on a square lattice with an identical pitch on each side of a principal lattice line along which the two lattices are relatively displaced by one half pitch. At the level of the expansion-bends, the two lattices are in interjacent relation, the tubes have substantially the same cross-section and the tubes of one row located at right angles to the principal line retain the same cross-section as in the rectilineal portion, extend into the other lattice in the plane of said row and pass between the parallel rows of the other lattice.

[1i] 3,732,922 1451 May 15,1973

United States Patent 1 Pouderoux HEAT-EXCHANGER MODULE l/l970Byerley...............................165/81X Inventor: PierrePouderoux, Paris, France Primary Examiner-Albert W. Davis, Jr. [73]Assignee: Stein Industrie, Paris, France A -Cameron, Kerkam and Sutton[22] Filed:

[57] ABSTRACT A tube bundle for the circulation of a first fluid is Feb.25, 1971 211 App]. No.: 119,124

disposed within a shell for the circulation of a second ForeignApplication Priority Data Mar. 6, 1970 fluid. At least one end of thetube bundle has a rectilineal portion followed by expansion-bends forFrance...,.................;.1.........1.700821 compensatingdifferential expansions. The tubes are Us CL Num-"mum.5/158, subdividedin the vicinity of the rectilineal portion into two half-bundles eachdisposed on a square lattice with an identical pitch on each side of aprincipal lattice line along which the two lattices are relativelydisplaced by one half pitch. At the level of the expan sion-bends, thetwo lattices are in interjacent relation,

8 2 0 N65 7 G 5., 11 F. ,8 ,8 i 53 2 96 f 81% 2N1 Fm h C r a e "S M 1 dLd .l .mF 1] 00 55 [.l.

the tubes have substantially the same cross-section [56] ReferencesCited and the tubes of one row located at right angles to the UNITEDSTATES PATENTS principal line retain the same cross-section as in therectilineal portion, extend into the other lattice in the X plane ofsaid row and pass between the parallel rows ml65/8l of the otherlattice. Fouche et al...........................122/32 3,171,4773,247,897 Ammon........... 3,431,893

5 Claims, 3 Drawing Figures 1 HEAT-EXCHANGER MODULE The inventionrelates to a heat-exchanger module of tubular type which can be employedalone but is preferably intended to constitute heat exchangers of largesize as a result of interassembly of identical modules.

It is known in particular that heat exchangers which are constructed byinterassembling standard units having smaller dimensions are employed inparticular for heat transfer processes between two fluids which areliable to give rise to violent reactions with each other in the event ofleakage. This problem arises in particular in heat exchangers which areemployed as steam generators in conjunction with nuclear reactors of thefast-neutron type the fluids between which the transfer takes place arein that case water which vaporizes and a liquid metal such as sodium.

In this case, the design concept of unit construction has the effect offacilitating the location of any leakage which may occur and thepossibility of isolating each module individually often avoids the needfor complete outage of the heat exchanger in the event of leakagemoreover, a leak which develops in any particular tube is less liable toresult in damage to a large number of adjacent tubes.

The present invention proposes a heat-exchanger module which meets thesedifferent requirements more effectively than the structures which havebeen adopted up to the present time. More particularly, the invention isintended to achieve a further increase in operational safety, especiallyby solving the problems of differential thermal expansions andvibrations, as well as to permit the construction of a module which hasa substantially uniform and compact external geometry and which canreadily be assembled with other identical modules in order to constitutea heat exchanger having a high output and small overall spacerequirements while ensuring a high degree of operational safety.

The heat-exchanger module in accordance with the invention comprises aplurality of tubes for the circulation of a first fluid which aredisposed in a bundle between two tube-plates within a shell for thecirculation of a second fluid and is provided at least at one extremityof said bundle with a rectilineal portion followed by expansion-bendsfor compensating differential expansions. The heat-exchanger module ischaracterized in that said tubes are subdivided at least in saidrectilineal portion in the vicinity of said tube-bundle extremity intotwo half-bundles each disposed on a square lattice with an identicalpitch on each side of a principal lattice line along which the twolattices are relatively displaced by l pitch. At the level of theexpansion-bends, the two lattices are disposed in interjacent relationand the tubes of each row which is located at right angles to saidprincipal line in each lattice retain substantially the samecross-section as in the rectilineal portion, extend into the otherlattice while forming the expansionbends in the plane of said row andpass between the parallel rows of the tubes of the other lattice.

In accordance with further characteristic features, the heat-exchangermodule is characterized in that it comprises a pipe for the discharge oradmission of said second fluid which is located at a sufiicient distancefrom said tube-bundle extremity to assist the circulation of said secondfluid away from the expansionbends, that said shell forms in thevicinity of said tubebundle extremity a chamber which has a largerdiameter than the bundle itself and which encloses the expansion-bendsand/or the tube bundle is surrounded within said chamber by a sleevewhich terminates at the level of the expansion-bends, said sleeve beingprovided with at least one opening through which the second fluid ispermitted to pass.

A particular embodiment which has been chosen by way of example in orderto provide an explanatory il lustration of the invention will now bedescribed with reference to the accompanying drawings, in which FIG. 1is a vertical sectional view of a heat-exchanger module in accordancewith the invention FIG. 2 is a diagrammatic sectional view of the samemodule taken along line A-A of FIG. 1.

FIG. 3 is a sectional view through the module of FIG. 1 to show thedistribution of the tubes therein.

The heat-exchanger module as illustrated in these fig ures is a unitarymodule which is intended to be assembled together with other similarmodules disposed in parallel so as to constitute a complete heatexchanger.

In the particular case under consideration, said heat exchanger is infact the steam generator of a nuclear power station in which a breederreactor is cooled by liquid sodium or another liquid alkali metal.During operation, heat is transferred by means of said heat exchangerbetween the hot sodium which is cooled and the water which is vaporized.

The heat exchanger is of the tubular type. As shown in FIG. 1, eachmodule is essentially constituted by a shell 1 which is normallyvertical and by a bundle of straight tubes 2 which are enclosed withinsaid shell. The ends of said tubes are welded to abottom tubeplate 4 anda top tube-plate 5, both tube-plates being located within the shell 1respectively at each end of this latter. The tubes are thus disposed inparallel relation on the flow path of a first heat-transfer fluid whichconsists in this case of water in the fonn of either liquid or steam.The second fluid which consists of liquid sodium circulates in contactwith said tubes within the shell 1. In order that the circulation shouldtake place in a predetermined flow pattern, an inlet pipe 6 is providedfor the admission of sodium into the upper portion of the module and anoutlet pipe 7 is provided for the discharge of the sodium at the lowerend whilst the water circulates within the tubes in the upward directionfrom a supply pipe 8 to a discharge pipe 9.

The vaporized water in fact passes out of the module in the state ofsuperheated steam. The module therefore has an upper section forming asuperheater above a lower section which constitutes aneconomizerevaporator. Moreover, the module: is so designed that thesuperheater section can placed in parallel with a resuperheaterconstituted by another module which may be of a different type. To thisend, the module as herein described is provided between the superheatersection and the economizer-evaporator section with an additional sodiuminlet 10 through which the sodium passes from the resuperheater andjoins the hot sodium stream from the superheater section at the inlet ofthe economizer-evaporator section.

At the level of each sodium inlet or outlet, the shell 1 is enclosed bya spaced wall to form chambers 11 having a larger diameter than thecylindrical portions of shell 1 which surrounds the tube bundle.However,

the cylindrical portions of shell 1 are extended respectively within theinterior of each chamber 11 by means of extensions l2, l3, 14,respectively, which protect the tubes from direct impact of the sodiumbut are nevertheless provided with one or a number of openings throughwhich the sodium is permitted to pass.

Moreover, the different tubes of the bundle are more closely spacedwithin the superheater section than within the economizer-evaporatorsection. In order that the same overall size of the shell 1 shouldnevertheless be maintained in both sections, provision is made insidesaid shell and within the superheater section for an inner sheath 16which surrounds the tube bundle, which is welded to the shell at theupper end of this latter and which limits the zone of sodiumcirculation.

In order to permit compensation for differential expansions duringoperation, the configuration of each tube of the bundle forms anexpansion-bend 18 near the lower end of the module above the bottomtubeplate 4.

The sleeve 12 which is provided around the tube bundle within the lowersodium-outlet chamber stops short of said expansion-bends and theselatter can thus take up the entire available cross-sectional spacewithin said chamber. Moreover, the result thereby achieved is to assistthe circulation of sodium away from said extension-bends which are thuslocated in a calm zone.

In this zone in which the tubes consequently have no further function inthe heat transfer process, a compact arrangement is obtained by virtueof an original distribution of the bundle tubes and by virtue of thearrangement of interjacent expansion-bends which is thus made possible.

In the rectilineal portion which precedes the expansion-bends in thevicinity of the lower end of the tube bundle, the different tubes aresubdivided into two halfbundles each disposed on a square lattice withan identical pitch on each side of a main lattice line along a diameterof the module. The geometry which is imposed at this end of the tubebundle is not necessarily retained in the remainder of the module.

As shown in FIG. 2, the two lattices conform to the same squareconfiguration and pitch but are relatively displaced by one-half pitchalong the principal line of separation. The expansion-bends formed bythe tubes of one lattice which form part of a same row at right anglesto said principal line can thus penetrate into the space of the otherlattice while remaining in said plane and while passing between twoparallel rows of tubes of the other lattice. It should be pointed outthat, at the level of the expansion-bends, the tubes still havesubstantially the same cross-section as in the preceding rectilinealportion.

The module as hereinabove described thus makes it possible to ensureeffective compensation for differential expansions by means of theexpansion-bends which are provided at the lower extremity but whichnevertheless do not call for any increase in overall size of the module.Positioning of said expansion-bends away from the normal sodium flowprevents vibrations.

The invention is naturally not limited in any sense to the particularembodiment which has been described in the foregoing but extends to allalternative forms.

What we claim is l. A heat-exchanger module comprising a plurality oftubes for the circulation of a first fluid which are disposed in abundle between two tube-plates within a shell for the circulation of asecond fluid and provided at least at one extremity of said bundle witha rectilineal portion followed by expansion-bends for compensatingdifferential expansions, wherein said tubes are subdivided at least insaid rectilineal portion in the vicinity of said tube-bundle extremityinto two half bundles each disposed on a square lattice with anidentical pitch on each side of a principal lattice line along which thetwo lattices are relatively displaced by one half pitch and wherein saidtwo lattices are disposed in interjacent relation at the level of theexpansion-bends and the tubes of each row which is located at rightangles to said principal line in each lattice retain substantially thesame cross-section as in the rectilineal portion and extend into theother lattice while forming the expansion-bends in the plane of said rowand passing between the parallel rows of the tubes of the other lattice.

2. A heat-exchanger module according to claim 1, wherein said modulecomprises a pipe for the discharge or admission of said second fluidwhich is located at a suificient distance from said tube-bundleextremity to assist the circulation of said second fluid away from theexpansion-bends.

3. A heat-exchanger module according to claim 1, wherein said shellforms in the vicinity of said tubebundle extremity a chamber which has alarger diameter than the bundle itself and which encloses theexpansion-bends.

4. A heat-exchanger module according to claim 3, wherein the tube bundleis surrounded within said chamber by a sleeve which terminates at thelevel of the expansion-bends, said sleeve being provided with at leastone opening through which the second fluid is permitted to pass.

5. A heat-exchanger module according to claim 1, said module beingemployed as a steam generator for the vaporization and superheating ofsaid first fluid, wherein the pitch of the tube bundle is smaller in thesuperheater section than in the evaporator section, said tube bundlebeing surrounded at the level of the superheater section by an innersheath which limits the zone of circulation of the second fluid withinsaid shell.

1. A heat-exchanger module comprising a plurality of tubes for thecirculation of a first fluid which are disposed in a bundle between twotube-plates within a shell for the circulation of a second fluid andprovided at least at one extremity of said bundle with a rectilinealportion followed by expansion-bends for compensating differentialexpansions, wherein said tubes are subdivided at least in saidrectilineal pOrtion in the vicinity of said tube-bundle extremity intotwo half-bundles each disposed on a square lattice with an identicalpitch on each side of a principal lattice line along which the twolattices are relatively displaced by one half pitch and wherein said twolattices are disposed in interjacent relation at the level of theexpansion-bends and the tubes of each row which is located at rightangles to said principal line in each lattice retain substantially thesame cross-section as in the rectilineal portion and extend into theother lattice while forming the expansion-bends in the plane of said rowand passing between the parallel rows of the tubes of the other lattice.2. A heat-exchanger module according to claim 1, wherein said modulecomprises a pipe for the discharge or admission of said second fluidwhich is located at a sufficient distance from said tube-bundleextremity to assist the circulation of said second fluid away from theexpansion-bends.
 3. A heat-exchanger module according to claim 1,wherein said shell forms in the vicinity of said tube-bundle extremity achamber which has a larger diameter than the bundle itself and whichencloses the expansion-bends.
 4. A heat-exchanger module according toclaim 3, wherein the tube bundle is surrounded within said chamber by asleeve which terminates at the level of the expansion-bends, said sleevebeing provided with at least one opening through which the second fluidis permitted to pass.
 5. A heat-exchanger module according to claim 1,said module being employed as a steam generator for the vaporization andsuperheating of said first fluid, wherein the pitch of the tube bundleis smaller in the superheater section than in the evaporator section,said tube bundle being surrounded at the level of the superheatersection by an inner sheath which limits the zone of circulation of thesecond fluid within said shell.